Abstract
Mixed oxide Ir-Sn-Sb-O electrocatalyst was synthesized using thermal decomposition from chloride precursors in ethanol. Our previous results showed that Ir-Sn-Sb-O possesses electrocatalytic activity for an oxygen evolution reaction (OER) in acidic media. In the present work, the physicochemical characterization and performance of Ir-Sn-Sb-O in an electrolysis cell are reported. IrO2 supported on antimony doped tin oxide (ATO) was also considered in this study as a reference catalyst. Scanning electron microscopy (SEM) images indicated that Ir-Sn-Sb-O has a mixed morphology with nanometric size. Energy dispersive X-ray spectroscopy (EDS) showed a heterogeneous atomic distribution. Transmission electron microscopy (TEM) analysis resulted in particle sizes of IrO2 and ATO between 3 to >10 nm, while the Ir-Sn-Sb-O catalyst presented non-uniform particle sizes from 3 to 50 nm. X-ray diffraction (XRD) measurements indicated that synthesized mixed oxide consists of IrO2, IrOx, doped SnO2 phases and metallic Ir. The Ir-Sn-Sb-O mixed composition was corroborated by temperature programmed reduction (TPR) measurements. The performance of Ir-Sn-Sb-O in a single cell electrolyser showed better results for hydrogen production than IrO2/ATO using a mechanical mixture. Ir-Sn-Sb-O demonstrated an onset potential for water electrolysis close to 1.45 V on Ir-Sn-Sb-O and a current density near to 260 mA mg−1 at 1.8 V. The results suggest that the mixed oxide Ir-Sn-Sb-O has favorable properties for further applications in water electrolysers.
Highlights
Hydrogen (H2 ) production has been achieved using different processes such as hydrocarbon reforming, photocatalytic generation, biodigestion, water thermolysis and water electrolysis [1,2].Water electrolysis (WE) is one of the most preferable processes since pure H2 can be obtained with the production of O2 as a secondary reaction [3]
The results showed that the polarisation curves for both catalysts are consistent with electrochemical impedance spectroscopy (EIS) results and other electrochemical measurements. These results indicate that Ir-Sn-Sb-O has better oxygen evolution reaction (OER) electrocatalytic properties than IrO2 /antimony doped tin oxide (ATO)
The higher electrical conductivity observed for Ir-Sn-Sb-O may be due to the presence of metallic iridium and to the doping of mixed oxide with antimony, which improves the electron transport through the material
Summary
Hydrogen (H2 ) production has been achieved using different processes such as hydrocarbon reforming, photocatalytic generation, biodigestion, water thermolysis and water electrolysis [1,2].Water electrolysis (WE) is one of the most preferable processes since pure H2 can be obtained with the production of O2 as a secondary reaction [3]. Hydrogen (H2 ) production has been achieved using different processes such as hydrocarbon reforming, photocatalytic generation, biodigestion, water thermolysis and water electrolysis [1,2]. Catalysts 2020, 10, 524 is separated into hydrogen and oxygen through the use of electrical energy. AWE presents several advantages such as a well-established technology, use of low-cost metals as catalysts and relatively low-cost materials for the system design. SPEWE is currently the most studied electrolysis process thanks to several technological features [7,8,9,10]: high current densities, high voltage efficiency, good partial load range, compact system design and high purity gas production. Water electrolysis requires an excess of energy (i.e., overpotential) to overcome activation barriers, and without a proper supply of this energy excess, hydrogen and oxygen are produced slowly [11]
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